1. Field of the Invention
This invention relates to packings and has particular but not exclusive reference to packings for use between the lid and body of a tank, for sealing the lid.
2. Description of the Prior Art
The packings in use at present for sealing the lids of tanks used to contain solvents and other liquid chemicals, e.g. on board ships, are in general made from plaited asbestos yarn impregnated with polytetrafluoroethylene (PTFE). Although these are resistant to most of the chemicals normally encountered, for example, in industrial or marine applications, the packings rapidly acquire a set and consequently leakage can occur after a lid (for example, a ship's cargo tank cover) has been opened and closed several times during service. Such packings are manufactured in a continuous length and are cut to the required length of the lid before being fitted. This means that leakage can also occur at the joint, particularly if this is not accurately cut or if shrinkage occurs during service thereby allowing the joint to open.